Hot Water Always On

We have a split system, Vaillant Boiler with a HW tank. Our electrician installed a wired smart thermostat for upstairs and downstairs to replace the old system.

Under the old system we only paid for hot water when we used it. Every other time of day our energy bill showed 0kwh.

Now with the new installation it is showing 60kwh every hour …. You can imagine how expensive this is!!!

Had the electrician done something wrong? Or am I doing something wrong? Do I need extra tado device to control the HW tank?


  • The only Tado device that can control hot water is the wireless receiver. I would contact the electrician and ask if there’s a separate, non Tado hot water programmer somewhere that you’re unaware of.
  • Something seems off with your numbers. I am going to assume that when you say your energy bill used to show 0kwh and now shows 60kwh every hour you are referring to a smart meter display unit rather than a printed paper bill.
    I cannot understand how it would be displaying 60kwh every hour. My boiler is one of Vaillants biggest ones - a 937 - it is rated at maximum output 37kw and so running at maximum for an hour would use 37kwh. I do not know of any Vaillant boiler rated at 60kw. Is your boiler actually running flat out all day as I'm sure your hot water tank would be boiling if it was. If your boiler is running flat out all the time I would be turning it off and getting a Vaillant engineer in rather than the electrician.
    If your boiler isnt running all the time is it possible it's the smart meter display that is the problem?
  • MelissaBrabanski
    edited November 2022
    Thats a typo on my behalf. It is reading at 0.60kwh every hour… not 60kwh!!

    After more investigation we can determine The boiler is running all the time, to heat the hot water tank.
  • Also, yes. Smart meter disply
  • GrayDav4276
    GrayDav4276 ✭✭✭
    edited November 2022
    I think that as @johnnyp78 says you need to get the electrician who installed your new thermostats to reassess what he's done.......I suspect that he has little knowledge of how the tado° system works.
    What other tado° devices do you have ?? 🤔
  • Managed to get the electrician back out this afternoon. It seems that there was something to do with the bridge on the boiler. He had not taken out the old one so it was constantly asking to heat the tank. Fingers crossed it’s made a difference. Time will tell tomorrow when my itemised energy bill comes through!!

    We got two smart thermostats (one as a starter pack with internet bridge) and four TRV.
  • Thank you for everyone’s help so far. Having tried to figure it out myself it was clearly a job for professional hands. I will let you know tomorrow if it’s fixed…. I can be hopefully!
  • Fingers crossed 🤞 🙏
  • @MelissaBrabanski unless the electrician has also installed a Tado wireless receiver (or there’s a pre-existing controller) you’re going to have no control over your hot water, so I would double check that theres something in place.
  • We have a Drayton timer for the hot water tank currently
  • That’s fine then, Tado will control your heating and the Drayton will control your hot water.